The present invention relates to improving the efficiency of emissions control equipment, and more particularly to a use of auxiliary generator exhaust to provide heat required for emissions control processes.
A variety of activities produce exhaust having harmful levels of emissions (or pollution.) Large stationary emissions sources may have co-located emissions control systems. However, some emissions sources are mobile, and require similarly mobile emissions control systems. An example of a significant mobile emissions source is an ocean going vessel. A single container ship may produce as much emissions as 12,500 automobiles. U.S. patent application Ser. No. 10/835,197 for “Maritime Emissions Control System,” assigned to the assignee of the present invention, describes a mobile emissions control system which may be transported to a ship within a harbor, and which mobile emissions control system captures and processes a main exhaust flow from the ship to reduce emissions. The main exhaust flow may be from the ship's engine(s), auxiliary generators, or any other source of exhaust from the ship. The emissions control system of the '197 patent includes a bonnet which is lowered over the ship's stack, and a rather long duct for carrying the main exhaust flow from the ship's stack to emissions processing equipment carried by a barge alongside the ship. As a result of the distance the main exhaust flow must travel before reaching the emissions processing equipment, the temperature of the main exhaust flow is much lower that it's temperature upon being exhausted from an engine or engines. The '197 applications is herein incorporated by reference.
The emissions control system processing equipment described in the '197 patent includes a first system for reduction of nitrogen oxides (NOx) as its primary purpose. The first system comprises four stages. The first stage comprises a Pre Conditioning Chamber (PCC) quench vessel. The second stage comprises oxidation column. The third stage comprises reduction column. The fourth stage comprises a caustic (or polishing) column.
Although a preferred system for reducing NOx emissions is a Selective Catalytic Reducer (SCR) system, the first system does not include an SCR system because using known SCR systems would require the addition of substantial heat. The main exhaust flow would require heating to a high temperature before introduction into the SCR system. Also, ammonia used by SCR systems is preferably generated by heating urea. The cost and space required for an energy source for heating, made such known SCR systems impractical for a mobile emissions control system.